Food spoilage and contamination

• What conditions are needed for microorganisms to grow?

  temperature, moisture, food, time, PH and Oxygen
• How can the growth of microorganisms be controlled?

  1. cook food thoroughly at high temperatures 75°C

  2. not leaving food in warm places

  3. cooling down left over food quickly with 90mins

  4. drying food

  5. preserving food with lots of sugar or salt, which removes water

  6. using food by its use-by date

  7. preserving the food in an acid to prevent microorganisms from growing and multiplying
• What foods are high risk?

  ready to eat, moist foods, usually high in protein that support the growth of pathogenic bacteria and do not require further heat treatment or cooking - Cooked Seafood or Chicken - Dairy foods
• How can enzymic action be controlled?

  blanching vegetables before freezing to denature enzymes

  using acids to denature enzymes, preventing browning

  Cold Temperatures
• How do moulds affect foods?

  - moulds have a furry appearence on the surface of the food

  - they multiply by sending out tiny airborn spores which land on food and germinate under favourable conditions

  - germinated spores send roots called mycelium into the food, and send up thousands of 'fruits' which are visible on the surface of the fruit

  - harmful waste products can spread into the food through the mycelium, which can be harmful if eaten
• How do yeasts affect foods?

  - they land on the food like mould and ferment it. yeast appears as pale brown, spotted growth on the skin of the fruit, which becomes brown and mushy as the yeast grows
• How are microorganisms used in food production?

  - moulds are used in the production of blue cheese

  - yeast is used to raise bread

  - bacteria is used to give the distinctive flavour to cheese and yogurt
• How are microorganisms used to produce blue cheese?

  Special mould spores are mixed with the cheese mixture, and later activated during maturation by poking with a metal rod to introduce air to the cheese
• What are the different possible sources of bacterial contamination?

  1. other contaminated foods

  2. work surfaces and equipment

  3. Food Handlers

  4. Pests - Flies, insects, birds, mice and rats

  5. Waste food and rubbish
• Where is campylobacter found?

  raw poultry and meat

  milk

  untreated (dirty) water
• Where is E.coli found?

  beef (especially minced)

  raw milk

  untreated (dirty) water
• Where is salmonella found?

  raw and undercooked poultry, eggs and meat

  raw milk
• where is listeria found?

  soft cheeses

  cheese made from unpasteurised milk

  salad vegetables

  pates
• Where is staphylococcus aureus found?

  people (especially hands, noses and mouths, on skin and in cuts and skin infections)

  raw milk

  cold cooked meats

  dairy products
• What are the symptoms of campylobacter?

  diarrhoea (often with blood)

  abdominal pain

  nausea

  fever
• What are the symptoms of E.coli?

  diarrhoea

  abdominal pain

  vomiting

  fever

  kidney damage or failure
• What are the symptoms of salmonella?

  diarrhoea

  abdominal pain

  vomiting

  fever
• What are the symptoms of listeria?

  flu-like symptoms

  can cause miscarriage in pregnant women or infect the unborn baby
• What are the symptoms of staphylococcus aureus?

  abdominal pain

  vomiting

  low body temperature
• How can cross-contamination be avoided?

  - separate raw and cooked foods

  - store high risk foods in sealed packaging or boxes to prevent them dripping on other foods

  - wash hands after handling high risk foods

  - use separate equipment for different foods or wash equipment thoroughly between different foods
• How can contamination of work surfaces and equipment be avoided?

  - clearing an cleaning work surfaces and equipment regularly

  - allow heavily soiled equipment to soak in hot water and detergent to make it easier to clean later

  - use clean hot water to clean equipment

  - a dishwasher uses hot water to clean dishes very effectively

  - air-drying equipment circumvents the use of a drying up cloth, which can be a source of contamination
• How can contamination from people be avoided?

  - wash hands including nails regularly when preparing cooking and serving food

  - tie hair back

  - wear clean clothes

  - do not cough, sneeze or spit near food

  - cover up cuts and sores with a blue, waterproof plaster

  - do not lick fingers or utensils whilst cooking

  - remove jewellery from hands and wrists

  - remove false nails or wear disposable gloves when cooking
• How can contamination from pests be avoided?

  - cover food to protect from flies

  - use deterrents to make prevent pests easily getting into the building (e.g fly screens, food nets, metal grilles over drains and electric fly killers)

  - keep animal feeding bowls and utensils separate from those used by people

  - do not allow pets onto kitchen work surfaces
• How can contamination from waste food and rubbish be prevented?

  - empty kitchen food waste bins regularly

  - keep the main food waste bin away from food preparation areas (preferably outside)

  - regularly wash waste bin with detergent and hot water

  - wash hands after throwing rubbish away

  - try to avoid wasting food - recycle where possible
• How can contamination from food packaging be avoided?

  - store food packaging in a clean, dry place away from pests

  - always check use by and best before dates

  - always check food packaging you buy is not damaged
• What temperature should food be frozen at?

  -18°C
• What temperature should food be chilled at?

  0-5°C
• What temperatures is the danger zone?

  5 to 63°C
• What temperature should food be cooked and reheated to?

  75°C
• How should a food probe be used?

  1. reset the food probe before use

  2. sterilise probe using antibacterial wipe (or another valid method)

  3. insert the probe into the centre, the thickest part, of the food

  4. do not touch the pan or tray with the tip of the probe

  5. leave the probe in place until the temperature stabilises

  6. temperature must reach 75 degrees or above

  7. temperature must remain at 75 degrees or more for at least 2 minutes

  8. sterilise food probe after use
• Keep hot foods hot (Buffet)

  63°C or above
• Best-before date


  "Best Before Date" is, according to the manufacturer, the last date by which a products flavour and/or quality is best. A best-by date denotes the period of time during which the manufacturer feels that their product will retain its original quality.

  Used on Long life products usually stored at Ambient temperature.
• Use by date


  The date when food is likely to be unsafe to eat and could cause food poisoning.

  Usually displayed on perishable foods such as raw and cooked meats and dairy.

  it is against the law to sell food afters it's use by date.